Problem with displacement on edge
This is more or less a problem with the UV unwrapping of the object.
Go to edit mode and check out the UV layout with the subsurface modifier on.
If it looks messed up, then try to unwrap the object again, or use &quot;Project from View&quot;. Only use project from view if you are not going to view the other side of the object. Play around with the UV layout until you get a nice result for the entire cube.